


Gigantic Problems Require Gigantic Solutions

by CirclesArePointless



Series: My submissions for the IFHeaven Wake Up Challenger event [4]
Category: Kaiju Girls - Fandom, Love Live! School Idol Project, Love Live! Sunshine!!, ウルトラシリーズ | Ultra Series
Genre: Action, Alternate Universe - Fusion, Breaking the Fourth Wall, Crack, Crack Crossover, F/F, Humor, Kaiju, Kaiju Girls
Language: English
Status: Completed
Published: 2021-03-10
Updated: 2021-03-10
Packaged: 2021-03-16 13:21:56
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,694
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29950605
Author URL: https://archiveofourown.org/users/CirclesArePointless/pseuds/CirclesArePointless
Summary: When yet another kaiju was unleashing its rage on the city, it was up to Mari and Rin to uphold their duty and counter the threat as Kaiju Girls. If only they were a bit more mindful of the city itself...
Relationships: Ohara Mari/Hoshizora Rin
Series: My submissions for the IFHeaven Wake Up Challenger event [4]
Series URL: https://archiveofourown.org/series/2180313
Comments: 2
Kudos: 2
Collections: Idol Fanfic Heaven's Wake Up Challenger Event 2021





	Gigantic Problems Require Gigantic Solutions

**Author's Note:**

> just to preface this with some context: https://myanimelist.net/anime/33011/Kaijuu_Girls__Ultra_Kaijuu_Gijinka_Keikaku  
> that's it. that's the entire context.  
> i can't believe i'm inventing the mari/rin tag for a crack crossover kaiju AU based on their seiyuu's role in that lol (really wished they were kaiju-sized in that anime though, but hey, that's why i'm writing this...)
> 
> my submission for the Easy-2 prompt of IFHeaven's Wake Up Challenger event: Write a rare pair (anything under 50 fics on Ao3 for µ’s and Aqours, 10 for Niji)

“Gao!”

Ah, what is Tokyo without kaijus terrorising its habitants every week or so? The most populous city in the world sure has a penchant for being an attractive target for these huge monsters, wreaking havoc and causing a huge dent in the city’s maintenance budget.

Today, the creature in question was about 15 storeys tall, its width almost equivalent to the wide boulevard it was walking on. Its intimidating size was enough reason to be concerned. The kaiju had scales for skin, bearing a shade of dark green one would usually see on reptiles. Its limbs had claws sharp enough to pierce metal, with equally sharp thorns lining its back. On the off chance that one even dared to look straight at its face, one could see feral eyes as red as its rage.

The giant growled again. Its movement was slow but deadly. For every stomp, the city was shaken to the core, as if they were hit by mini earthquakes. Humongous footprints desecrated the asphalt of the streets. The creature even left a mark of destruction behind, in part due to its tail wagging continuously.

Buildings were toppled from their foundations. Flames were set ablaze. Everybody was running away from the threat, screaming for their lives; although by now, they had gotten too used to it that it felt more like a chore instead. A routine ingrained in their habits.

Inside one of the many glass-clad skyscrapers, Nico was sitting behind her desk in the comfort of her own office. The raven-haired girl currently runs an idol agency, and right now, she was keeping track of the latest trends and the popular perception of the acts under her wing. Sometimes, she would be so focused on her tasks that anything around her, no matter how major and disruptive, would be left unnoticed.

That was, until blinding flashes of red filled the room, accompanied by a blaring alarm.

The panic-inducing sounds and sight were the ones to finally shake Nico out from her trance. A look outside was enough to justify them, luckily the ruckus was happening at a safe distance. However, that didn’t mean the threat was any less significant. Without hesitating, she rose from her leather chair and rushed towards a nondescript grey wall, before staring straight at a poster of herself, specifically at the red eyes.

Nobody knows Nico more than Nico herself.

Suddenly, the wall split into two, revealing a metallic compartment resembling that of an elevator interior. She quickly rushed inside, preparing herself for a long descent.

It might seem that this secret elevator served as an escape route for the all-important big boss, but actually, it served a different purpose. This lift would carry Nico straight underground, where a different office awaits her.

To counter humongous threats like the kaiju outside, a special task force was established. Conventional weapons proved its futility no matter how mighty they were, and obviously the higher-ups were hesitant on unleashing dangerous weapons that could also pose a huge risk to innocent people.

Instead, they resorted to alternative methods, like having a division of specially trained soldiers. They were equipped with weapons advanced enough to subdue monsters like the ones rampaging outside. But sometimes, you just got to fight fire with fire.

Nico’s part in this organisation was leading a division consisting of kaiju girls, namely girls who possessed the souls of kaijus before them. These girls could likewise summon their inner monster and transform into a hybridised form based on the kaiju they inherited. With proper training, they could be nurtured to become a useful asset in neutralising these huge threats.

In fact, Nico herself was one, but Pigmon, the kaiju she inherited, was passive by nature, which meant that she wasn’t fit for combat. She was instead delegated (or rather, relegated) to a management role. Well, not that it mattered, she would rather spend her time under here than getting into a heated combat.

She would soon reach the main quarters, where wide screens displayed the magnitude of the attack. Nico needed to be well informed of the situation to avoid misgauging the threat and making ill-informed decisions.

After she was done analysing the information provided, Nico shouted a command at the task force’s android system, hoping that it would clear things up for her.

“Threat Report!”

Silence was her only response, prompting Nico to shout again, but louder.

“Threat Re—”

Before Nico could finish her sentence, the machinery beeped to life, followed by a sweet, synthesised voice that somehow reminded her of an old friend.

“Threat level: high. However, I could not find any prior information about it from the database. Therefore, I am unable to accurately gauge the monster’s power level or its exact weaknesses.”

_Gee, she really does sound like Umi. Did the programmers hired her to recite all the syllables?_ Nico shook her head back to reality. “Huh, a new monster…”

“Yes. Judging from the footage, this kaiju proved itself to be very dangerous and I recommend immediate action.”

“Any of our girls nearby?”

“Yes. Two in fact.”

One of the screens displayed a zoomed-in map, showing her the location of the attack, as well as where the girls were and their identities.

Two is better than one they say, so Nico already had her hopes up for a mission easily accomplished despite the rather unknown threat. However, all that turned into worry the second she saw their names on the screen. From their past battles, these two were infamously known to be reckless, chaotic, and probably causing as much damage as the opponent they were fighting against. Pitting the two with each other? That’s a catastrophe waiting to happen.

_Aah, how am I gonna explain this..._

Unfortunately, there was nobody else in the vicinity, leaving the director with no choice. Sigh. If Nico were to ever get called up by her higher-ups to explain this mess, then she would rather flee away from them with a red balloon.

“Send them the alert,” commanded Nico, masking her doubts with an urgent tone.

The computer beeped in place of a nod.

\----

The clear sunny skies were a perfect backdrop for a lovely day out. At the storefront of a tea house, Mari and Rin were seated at one of the tables, sipping their bubble tea and enjoying each other’s company.

The two had been together for quite a while, starting from a strictly professional relationship to a more casual one. They began to spend more and more time together, oftentimes hanging around at expensive places, all thanks to Mari’s bottomless wallet. It made Rin feel guilty sometimes, but all that feeling instantly dissipated whenever her partner told her that it was all fine.

The couple exchanged a fair share of empty chatters, all ears for even the most mundane things ever said. They were now considering the possibility of living together (or rather, Rin moving into Mari’s place which could actually fit at least four more), ecstatic at the prospect of being at each other’s side more often.

“Look, look!”

Mari curiously turned her yellow eyes to the ever-exuberant Rin. “What is it?”

Rin then shoved her phone almost directly at Mari’s eyes. On the screen, Mari could observe a pair of cat ears, the accessory adorning different shades of pastel pink as well as what looked like soft fluffy fur on its edges.

“These cat ears! They’re just so cute, nya…”

“Oh, they are…” Mari smirked.

“Kayo-chin really has a good eye for something like that. Though, it’s kinda expensive…”

“Expensive? What’s that?”

Rin couldn’t tell if her filthy rich girlfriend was genuine with her question or was just simply teasing. She decided to stay silent, letting the blonde to continue talking.

“But either way, you’re already cute as it is.”

Mari slowly extended her arm towards the girl.

“Who’s the good girl?” She patted Rin’s head a few times before playfully stroking her orange hair, eliciting a purr from her feline-esque girlfriend.

However, the sugary display of affection came to a sudden halt when both their smartphones buzzed.

Almost simultaneously, they grabbed their devices up from the table, looking for what felt like an important notification.

“Oh, there’s a severe threat nearby apparently,” Mari remarked.

Their smartphones were actually standard-issue Soulrisers, a device that doubled as both a high-end smartphone and a transformation device that allows them to transform into their kaiju form safely.

“You don’t need a Soulriser to see that, nya.”

Rin spun Mari’s head around to face said threat.

The bright sun was now overshadowed by the raging kaiju, its shadow already proven to be a better shade than the small umbrellas strewn around the terrace. Oh, that’s a severe threat alright.

On one hand, Mari and Rin had every right to be angry for the monster to ruin their date like this, but on the other hand, maybe this could help spice it up instead. It didn’t matter that the alert didn’t specify much about its details, isn’t it more fun to just fight something without knowing much about it?

Leaving their beverages unfinished, they both ran to a nearby park, wanting to cause the least nuisance. They learned a big lesson after transforming in an alleyway last time out.

Amidst the plain green of the park, they both swiped upwards on the device’s screen while reciting the familiar words to call out the monsters within them.

“Soul Ride!”

Blinding lights enveloped their bodies, obscuring their transformation process from the general public.

Rin began to grow in size, her height almost matching the rampaging kaiju. Although she maintained a distinctly human figure, she began to display characteristics of Agira, the kaiju whose soul was inside her. Claws replaced nails as parts of her skin gradually became scaly. A long tail appeared from behind, followed by a sharp horn on her forehead.

Mari too had grown into monstrous proportions, being almost just as tall as her colleague. She however possessed different traits, representing Miclas instead. Instead of scales, her skin was turning more leathery than usual, darkening into a shade of brown. Four wavy horns protruded upwards from her blonde hair, and her hands and feet got bulkier.

Once the transformation was complete, the two girls were battle ready, roaring loudly just for the sake of it.

Of course, the loud noise had certainly attracted the attention of the mean green kaiju, who quickly turned its head towards them.

That was definitely part of the plan. _Definitely._

It was better to move the fight away from built-up areas anyways, so they just rolled with it. Besides, this park was wide enough for it to be a safe battleground for giants.

The kaiju, however, was irritatingly slow, much to the dismay of both Mari and Rin. They waited for what felt like eternity. On the plus side, at least people would have enough time to evacuate the scene.

It was only after a few minutes that action finally arrived. The beast attacked first, unleashing a powerful fist at Rin. The orange-haired girl managed to block it with her arms, the impact creating a deafening thud.

Mari then made her move, punching the creature away after catching it off-guard. Her thick fists were enough to drive it away at a distance, giving them ample time to rethink their strategies (if they even had any).

“I don’t know about you Rin, but this kaiju is _hella_ slow.” Mari managed to sprinkle some gratuitous English in her lines.

Rin only meowed back in agreement. Guess they found out one of its weak points already.

There was no rush to move quickly, and besides, running around would just cause the ground beneath them to tremble. So instead, both Mari and Rin took gentle steps to the fallen beast, hoping to subdue it as soon as possible.

Despite its tardiness, the scaly giant got up just in time, letting out a roar that shattered the glass on nearby buildings. This kaiju was ready to unleash its vicious rage.

They all traded concussive blows with each other, each punch much stronger than the previous one. This feral monster showed itself to be a tough fighter, being able to withstand a barrage of attacks from its opponents, but so were the two kaiju girls.

It was a clash of titans, fought at a massive scale. Punches and kicks were thrown around liberally, and neither side were willing to give up, even if the whole city were to devolve into ruins.

It was so intense until Mari and Rin were completely oblivious to the destruction beneath them. They were both so into the battle that they hadn’t realised that their fight had shifted to the fringes of the park, thereby affecting the buildings lining up the street beside it.

It was still as clear as day up above, but dust and fumes had already begun to permeate the air around their knees.

Frustratingly, the battle was caught in a stalemate. Despite the difference in numbers, it seemed like no side had the advantage.

Tired of the deadlock, Rin leaped with all her might, lunging herself straight onto the kaiju. When they both smashed themselves onto the ground, the resulting impact was immeasurable. Large cracks radiated from where their bodies collided with the earth. Firm structures flattened into mere rubble. More soot and dust filled the air.

It might seem that victory was finally theirs and the city was saved (albeit with a cost), but as it turned out, the battle was far from over.

Suddenly, the green kaiju rose from the ground, flinging Rin over and onto Mari, who just happened to be behind her. They both crashed onto the ground, again, causing tremors around them.

Rin quickly stood up though, she would do whatever it takes to take this threat down. Its roars only drove her to fight harder. And to roar equally loud too, although hers sounded more like an angry cat.

The scaly giant however only stood still at where it was, much to her concern. It felt eerily immobile. Eventually, the beast opened its mouth wide, but not to growl or roar.

Mari, who was still lying over the grassy ground, suddenly realised the danger her girlfriend just put herself into.

With barely a second to spare, a powerful beam of pure light emanated from the open mouth, headed straight for Rin.

Mari quickly jumped back up, putting herself in between the two giants. Fierce determination was seen in her yellow eyes as she too opened her mouth.

“SHIIIIIIIIIIIII—”

Another beam of shining light came from her mouth, countering the deadly ray from the kaiju. These two beams met at the middle, intensifying into a ball of heat rivalling that of suns. The deadlock was only broken when Rin shook herself out from her shock, ramming her horn onto the kaiju’s body.

“—NYYYYY!”

Mari managed to shut her mouth before her beam strayed somewhere else, barely grazing over the rooftop of a building. Meanwhile, Rin’s horn had pierced itself deep inside the creature, giving her the upper hand. She then moved her head upwards, tossing the humongous creature into the skies.

After a while, gravity pulled the creature back down, splashing violently into the big lake in the middle of the park. The water even splashed its way outside of the park’s perimeter, somehow helping to quell some of the flames out there.

The kaiju was battered and bruised, the effects of the seemingly never-ending battle finally showed itself.

Rin carried the almost lifeless creature back up, followed by her girlfriend on the other side. They both grasped onto its arms with as much restraint, and rightfully so as the beast tried to break free with all its might.

Of course, it got harder to restrain the kaiju as the minutes tick by; if one of them lost their grip, it would be back to square one all over again.

“Uhh, how long are we just gonna hold on, nya?”

“ _Just… patience!_ ” Mari said in English, blatantly disregarding the laws of grammar.

They held on tight for as long as they could, until eventually, a beam of blinding light appeared, targeted right at the kaiju.

“Riko-chan beam!”

The beam was extremely hot, fatal even, to the point where the kaiju just straight up disintegrated. Finally, the battle was over.

This left just Rin and Mari at the site, who then turned their heads towards where the light had just come from. At a distance, there stood their deus ex machina, an ultra-tall feminine figure whose skin looked like it was painted with patterns of silver and red. Two broad oval-shaped eyes decorated the metallic face, with a crest just on top of her head. All while her arms were crossing each other at a straight 90-degree angle.

“Well, where have you been this entire time?” Mari teased.

“Uhh, busy…” It was hard to tell if her face was blushing in this Ultra form, but the tone of her response had made it very clear that she was flustered. Riko would rather just leave it like that, for her delay was caused by something far more shameful and embarrassing than she would like to admit.

\----

**Several minutes ago…**

Riko was resting peacefully on her bed, reading the doujin she had only picked up a few days ago. There was no reason to be distracted; it was a lazy weekend, the sun outside was shining, and from the looks of it, no monster or alien would be here to disrupt the general peace.

Her amber eyes were completely focused on the paper; for a volume she had only picked up recently, she had gotten quite far into the story already.

“There’s a big attack going on outside!”

Of course, her day had to be ruined just like that by the Ultra alien who merged with her.

“Give me a minute, I’m almost done…” Riko groaned.

But the voice inside her head refused to yield.

“We have to go now!”

“Just one more page, okay?!”

When she turned the page, the chapter ended with a climactic cliffhanger, which only made Riko wanting to continue further. And because she hated stopping her read midway into a chapter, it might seem like she would be reading more than a page before she would spring into action.

The Ultra voice simply groaned, wondering why it was such a good idea to fuse itself with a doujin-crazed woman.

\----

**Back to the present…**

Almost immediately, a huge yellow flying machine entered the scene. It resembled that of a helicopter, but much grander in stature, and much more mechanical.

The craft came to a halt somewhere near the standing titans, clearly overshadowed by them. Suddenly, a familiar voice was heard from its speakers, loud and clear.

“Property damage is—” Mechanical limbs suddenly protruded from the craft, crossing each other in the shape of an X. “—BUU BUU DESU WA!”

“What? We tried our best, nya.” Rin said, dejected that their victory wasn’t well-received by the craft’s pilot.

“Yeah. And you’re in the wrong franchise anyways.” Mari playfully interjected.

“Does it matter? It’s still a tokusatsu. Look, I’ll let you know that I was involved in the Ultraman franchise if anything. And Kamen Rider too!”

“ _Ooh, flex._ ” Mari popped her lips. “What’s next, you’re gonna tell me you DJ in your spare time?”

“Uhh…” Dia sneakily pushed her turntable back into the dashboard, putting a premature stop to the lit remix of Tokimeki Bunruigaku that was playing inside the cockpit. Meanwhile, her other hand was scratching her beauty mark just under her lips. “No…”

The teasing stopped when a blinking red was flashing from Riko’s chest. It was about time as she couldn’t stay in her Ultra form for a prolonged period.

“Uhh, I think we should change back now that everything’s settled.”

The kaiju girls nodded. In just moments, they all changed back to their human forms.

Now that the three of them were normal-sized, only now did Mari and Rin realise the scale of destruction being wrought upon by their battle. No wonder their boss was always so uptight during the much-dreaded post-battle debrief.

As they walked along the avenue of ruins, the three of them swore that they saw a lone figure struggling to move itself. Alarmed, they all rushed towards the site.

Amidst the rubble, they all saw an orange-haired girl barely unconscious.

“Chika-chan, are you okay?” Riko asked.

“Huh…” The girl in question struggled to open her eyes, but when she did, a shade of red eerily similar to the kaiju’s eyes from earlier surrounded her pupils. The girl took a closer look at the ruins around her.

“Did, did I do all this?”

“What... do you mean, nya?” Rin was surprised to hear that coming out from her mouth.

Chika figured that it was difficult to explain it, so instead she muttered a barely audible reminder to herself.

“Ugh, note to self: don’t eat glowing mikans. Ever.”

To lighten up the mood, Mari thought that it would be a good idea to spend some time together.

“Hmm, you guys fancy some bubble tea? It’s all on me!”

“Hey, what about me?” Rin was surprised to see her girlfriend willing to splurge for someone else other than her.

“You’ll get an extra drink.” Mari pushed her tongue out.

Everybody simply nodded. Luckily, it wasn’t that far away from here, but when they did reach the location, all they could do was to just gape.

The tea house from before was all in ruins.

“Mari-san, what did I tell you about property damage?” Mari felt a sudden touch on her shoulders, turning to look at Dia who had just sneaked behind her.

All hope however was not lost. “I know another place, nya.”

Everyone agreed without putting much thought, Dia included. Leaving the scene, they all walked together with smiles on their faces and empty chatters filling their ears.

“Hey, we might as well invite Nico-chan over,” whispered Rin.

“Why not.” Mari dialled the direct number, hoping that a bubble tea offer would be more than enough to spare them the lecture.

**Author's Note:**

> so, if you all were wondering how they looked like, just imagine these with the relevant LL girl but maybe a lil bit more like their kaiju counterpart:  
> https://kaijugirls.fandom.com/wiki/Aki_Miyashita (Agira - Rin)  
> https://kaijugirls.fandom.com/wiki/Miku_Ushimaru (Miclas - Mari)
> 
> also, sorry if i messed up with the ultraman lore, it's been a while since i watched them (used to like, watch it regularly as a kid, but now i had to watch a few episodes just to re-familiarise myself lol)


End file.
